For many years, chicken and other poultry were processed for sale and human consumption largely by skilled butchers using a variety of sharp knives and other specialized hand tools. Recently, however, the development of automated poultry processing equipment has dramatically increased the speed and efficiency of poultry processing and has thus provided the consuming public with high quality poultry products at reasonable prices.
Most modern poultry processing equipment is designed for use along an overhead conveyor system having an array of spaced depending shackles from which poultry carcasses are suspended by their legs and conveyed along a processing path. Various processing machines are disposed along the processing path for operating upon the suspended carcasses progressively as they move along the path to prepare the poultry for public sale and consumption. A typical poultry processing line might, for example, include a vent cutter, a bird opener, an eviscerator, a neck breaker, a lung puller and a crop remover. In addition, such a processing line might include machines for subdividing poultry carcasses into their various commonly consumed pieces such as breasts, backs, wings, legs, and thighs.
One particular processing step that has proven especially challenging to automate has been the separation of the legs of poultry carcasses from the back portions of the carcasses. This separation is to occur at the thigh joints of the birds. The difficulty in automating this step has resulted in part because of the dense muscles and tough tendons that hold the thigh joints of the poultry carcasses together and the very tightly coupled nature of the ball and socket thigh joints themselves.
Some prior attempts to separate legs from backs have involved cutting through the carcasses at the thigh joints with rotary blades. While cutting the thigh joints in this manner does indeed separate the legs from the back, it usually results in a part of the peritoneum and some fat being left on the legs, which is highly undesirable to the consuming public. Further, such cutting usually severs the bones of the thigh joints rather than separating the joints, thus leaving at least a portion of the joint oyster on the back portion of the carcass. The oyster should remain intact on the end of the thigh bone for a neat appearance and to prevent leakage of marrow from the thigh bone into the edible meat.
Other previously employed methods for separating poultry legs from backs have included pulling the legs from the back rather than cutting through the joint. An example of such a method and an apparatus for performing the method is illustrated in U.S. Pat. No. 4,939,813. While such methods and devices represent an improvement over cutting or slicing through the thigh joints, they nevertheless have exhibited a number of problems and shortcomings inherent in their own respective designs. For example, the pulling apart of the thigh joints in such devices can and often does result in the oyster being left with the back portion of the carcass because of the tightly coupled nature of the joint. Further, the cleanliness of the separations effected by these devices has often not been completely acceptable.
Accordingly, a continuing and heretofore unaddressed need exists for a method and apparatus adapted to be used along an automated poultry processing line for reliably and cleanly separating the backs from the legs of poultry carcasses moving along the line. Such a method and apparatus should provide clean separations at the carcass thigh joints and should consistently and reliably leave the oysters of the joints attached to the separated ends of the thigh bones. It is to the provision of such a method and apparatus that the present invention is primarily directed.